Abstract: With the prevalence of smart phones, location based services (LBS) have received noticeable attention and has become prominent and vital. Despite the use of LBS, it also poses a serious concern on userís location privacy. In this paper, we propose a safe tourist application for privacy preserving spatial range query. The aim is to outsource the location based service (LBS) data from the LBS provider to the cloud and from the cloud to the LBS user without any privacy breach. To achieve privacy preserving spatial range query, we propose the first predicate only encryption scheme for inner product range, which can be used to detect whether a position is within a given circular area in a privacy-preserving way. To avoid scanning of all POIs to find matched POIs, we further exploit the novel index structure named ss tree, which conceals sensitive location information with our IPRE scheme. In particular, for a mobile LBS user using an Android phone, around 0.9 second is needed to generate a query.

Keywords: Location based services (LBS), spatial range query, point of interest (POI), Inner product range(IPRE).